A continuing demand exists for simple, inexpensive, mechanical devices which can be used to measure the depth of a body of liquid and to retrieve samples from the body so that the presence of contaminants in that body and/or characteristics of the liquid can be ascertained. Such devices are commonly used to measure the amount of fuel remaining in a storage tank, to ascertain whether there is water and/or foreign substances in the storage tank, to measure the depth of water in ship's bilges, and for other purposes familiar to those to whom this specification is addressed.
Devices of the character just described which resemble mine to some limited extent in appearance and/or in the capabilities they possess have heretofore been proposed. Those of which I am aware are disclosed in U.S. Pat. Nos. 200,981 issued Mar. 5, 1878, to Cox for COMBINED HYDROMETER CUP AND THIEF; 832,164 issued Oct. 2, 1906, to Rutenber for CASK OR TANK GAGE; 1,621,857 issued Mar. 22, 1927, to Seraphin for AUTOMATIC TANK GAUGE; 1,769,533 issued July 1, 1930, to Nash et al. for GAUGE STICK; 2,203,019 issued June 4, 1940, to Johnson et al. for GAUGE; 2,593,830 issued Apr. 22, 1952, to Baker for LIQUID SAMPLER; 3,169,322 issued Feb. 16, 1965, to Milo for COMBINED GAGE AND SAMPLER DEVICE; and 3,390,463 issued July 2, 1968, to Hirsch for LIQUID-LEVEL GAGE and in 1906 British patent specification No. 24,402 (Adamson).
For the most part, the patent documents identified in the preceding paragraph disclose devices which include an elongated tube or barrel with a spring biased valve at its lower end. Pressing the device against the bottom of a receptacle containing the liquid of interest opens the valve, allowing the liquid to flow into the tube until the level of liquid in the tube is the same as the liquid level in the receptacle. The subsequent release of downward pressure on the device allows a cooperating spring to close the valve, trapping the thus sampled liquid in the tube. That component is typically fabricated from a transparent material, allowing the operator to visually check for foreign substances in the liquid of interest.
In many instances, the contaminant may be present as a separate layer; and the existence, location, and thickness of the layer may be items of importance. Stratification cannot be maintained when a device as just described is employed to draw a sample because of the relative movement between the contaminant and the liquid of interest that inevitably occurs as the liquid and contaminant flow upwardly into the sampling tube of the device through the valve in its lower end.
Baker U.S. Pat. No. 2,593,830 does disclose a liquid sampling device which eliminates the just-discussed problem because the valve of that device is latched open until the device reaches the bottom of the receptacle and the latch is tripped. However, the Baker device lacks versatility in that there is no provision for first lowering the device and then opening the valve when the bottom of the body of liquid is reached as is desirable when it is those impurities at the very bottom of the liquid containing receptacle that are of interest.
Another disadvantage of heretofore proposed devices of the character in question is that the actuator is located beneath the liquid inlet and drain opening in the valve seat and must be displaced upwardly to open the valve and drain the sample from the tube. If the operator does this with his hand, the escaping liquid may soil him or cause even more severe problems if the liquid is corrosive, for example.
On the other hand, this heretofore employed location of the valve actuator does not lend itself to positioning the tube over an access opening and then opening the valve to drain the liquid back into the receptacle from which it was drawn unless the operator does use his hand to open the valve. There is nothing against which the valve actuator can be butted to displace it and thereby open the valve.
Another common deficiency of heretofore available liquid sampling devices is the absence of a visual, audible, or other indication to the operator that the flow of liquid into the tube of the sampling device has ceased and that the taking of the sample is therefore complete. The advantage of such an indication is important and self-evident.